Alzheimer's disease (AD) is the most prevalent form of dementia. This neurodegenerative disorder is characterized by two major pathologies, β-amyloid deposits and neurofibrillary tangles. Clinically, AD is characterized by the loss of memory, cognition, reasoning, judgement as well as orientation. As the disease progresses, further abilities are lost until a global impairment of multiple cognitive functions occur. These cognitive losses take place gradually, but typically lead to severe impairment and eventual death in 4-12 years.
β-amyloid deposits are predominantly formed from aggregated Aβ peptide. The Aβ peptide is formed from amyloid precursor protein (APP) through two independent proteolytic events involving β-secretase followed by γ-secretase. Variability in the site of proteolysis via γ-secretase results in Aβ species of variable length, the most predominant forms of which are Aβ38, Aβ40 and Aβ42. The secreted Aβ then aggregates into oligomeric species, which further aggregate to ultimately form the Aβ deposits detected in the brains of AD patients. The aggregated oligomeric species are widely believed to be the key neurotoxic agent responsible for the neurodegeneration detected in the brains of AD patients. Of the various Aβ species generated by γ-secretase, Aβ42 has been demonstrated to be the most aggregation prone as well as the most neurotoxic Aβ species. Furthermore, human genetics strongly supports a key role of Aβ42 as a key mediator of AD pathogenesis. More than 150 different mutations causing familial AD are known which result from either an increase in the ratio of Aβ42/Aβ40 peptides produced or increase the intrinsic aggregation propensity of Aβ. Based on this knowledge, therapeutic approaches aimed at lowering levels of Aβ42 are considered promising.
β-amyloid deposits and vascular amyloid angiopathy have also been characterized in the brains of patients with Trisomy 21 (Down's Syndrome), Hereditary Cerebral Hemorrhage with Amyloidosis of the Dutch-type (HCHWA-D), and other neurodegenerative disorders.
γ-Secretase inhibitors completely inhibit the cleavage of APP as well as all other substrates of γ-secretase. This inhibition leads to a simultaneous inhibition of the production of all Aβ species. As opposed to γ-secretase inhibitors, γ-secretase modulators preferentially block the production of the neurotoxic Aβ42 species while not inhibiting APP cleavage and thereby the generation of all Aβ species. Furthermore, γ-Secretase modulators do not inhibit the cleavage of other γ-secretase substrates, thereby diminishing the possibility of side effects.
WO 2010/132015 discloses compounds of the following core structures interfering with γ-secretase and/or its substrate
and their use as medicaments in the treatment of various diseases inter alia Alzheimer's disease.
WO 2011/014535 discloses compounds of the following core structure
which modulate β-amyloid peptide production and their use in the treatment of Alzheimer's disease.